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Showing results for tags 'basic engine checks'.
Hi, I've been hunting and chasing my tail to get some kind of throttle response from my wrangler above 45 MPH. I know these are not very powerful to start but I feel like what I'm experiencing is abnormal. Anywhere above about 45MPH when throttle is given There is little or no response from the engine. I have gone through the tuning and troubleshooting, replaced numerous things and adjusted what is able to be adjusted to the best of my understanding. Most recently I put a new cylinder head on due to a cracked web between valves on cylinder 4. I was so sure this was going to solve my issue considering the cylinder was down to 70psi compression. Though the engine runs smoother and quieter now it still is lagging at higher speed. 5th gear is pretty much useless unless going down hill. I have access to a modis scan tool so I can see ecu data. What is bothering me at this time is the engine rpm's are reading about 400 rpm's lower than my tach. Idling around 575 rpm's according to the scan tool data but reading around 1000 on the tach. In my opinion it feels like it is closer to the 1000 rpm range but I don't have a way to check it at this moment. My question is where does the ECU get the engine speed? is it from the ICM or the CPS? If its the cps can the cps fail in a way that it still reads but reads low? I may be barking up the wrong tree and I likely am. but right now I'm trying anything i can think of. Any other suspected areas to check? Any scan tool data that would be more important than others? Any suggestion is welcome. Thanks Dan